Why is one side of the face fuller while the other side appears flatter?

Under normal circumstances, facial asymmetry—where one side of the face appears fuller and the other sunken—may be related to genetic factors, eating habits, oral diseases, muscle atrophy, mumps, and other causes. Individuals experiencing facial discomfort should seek timely medical evaluation and appropriate treatment. Specific analyses are as follows:

1. Genetic Factors

Asymmetry in fullness between the left and right sides of the face is primarily due to hereditary factors affecting cheekbone height and abnormal distribution of soft tissues. This leads to asymmetrical cheekbones and uneven soft tissue thickness, resulting in one cheek appearing fuller while the other appears hollowed. For severe cases, improvement may be achieved through procedures such as cheekbone reduction surgery or liposuction, following medical advice.

2. Eating Habits

If a patient habitually chews food using teeth on one side, the facial muscles on that side may become more developed, leading to one side of the face appearing fuller than the other. If symptoms are mild, no special treatment is usually required. However, for patients with higher aesthetic demands, treatments under medical guidance may include injecting slimming injections (e.g., botulinum toxin) into the fuller side to reduce masseter muscle size, or performing augmentation on the sunken side via hyaluronic acid or autologous fat injections.

3. Oral Diseases

When oral diseases are present—such as severe gum infections causing swelling—one side of the face may appear swollen while the other remains normal or sunken. For periodontal disease, initial treatment under medical supervision may involve medications such as metronidazole tablets or amoxicillin capsules. Root canal therapy may be necessary in more advanced cases.

4. Facial Muscle Atrophy

If the facial nerves or muscles are damaged, or if they are chronically irritated by inflammation, facial muscle atrophy may occur, leading to asymmetry with one side appearing fuller and the other thinner. It is recommended to take medications such as vitamin B12 tablets or mecobalamin tablets as directed by a physician to alleviate symptoms caused by inflammation.

5. Mumps

Mumps is typically an acute respiratory illness caused by the mumps virus. Besides causing facial asymmetry with one side swollen and the other not, it may also present with symptoms such as headache, fever, and salivary gland enlargement. Patients with mumps should rest in bed and remain isolated until the swelling subsides. For those with body temperature exceeding 38.5°C, antipyretic medications such as ibuprofen sustained-release capsules or acetaminophen tablets may be administered according to medical instructions.

In addition to the above, unilateral facial fullness or hollowing may also result from facial muscle injury, congenital developmental abnormalities, and other causes. After ruling out congenital factors, individuals are advised to seek prompt medical evaluation. If facial asymmetry is caused by an underlying disease, timely consultation with a doctor and targeted treatment are essential. Maintaining good dietary habits and proper oral hygiene in daily life is also important.